[Show abstract][Hide abstract] ABSTRACT: Early identification of nonresponders to clopidogrel may be important in identifying subgroups of patients that might be at risk for future thrombotic events.
We prospectively assessed postclopidogrel platelet reactivity in 250 consecutive patients scheduled for elective percutaneous coronary intervention (PCI). All patients received dual antiplatelet therapy with 160 mg aspirin and a 300 mg loading dose of clopidogrel >12 hours before PCI. A platelet aggregation test was performed at the time of the intervention using a point-of-care assay, the Platelet Function Assay (PFA-100C/ADP; Dade-Behring, Deerfield, IL). Nonresponders were defined as having a PFA closure time of <71 seconds under dual oral antiplatelet therapy, reflecting normal platelet reactivity. Myonecrosis post-PCI constituted the primary end point and was defined as the release of creatine kinase-MB >1x the upper limit of normal on a sample taken 12 to 24 hours after intervention. The secondary end point was a composite end point of major adverse cardiac events including death, myocardial infarction, and stent thrombosis after 6 months.
The PFA closure time was available in 242 patients and ranged from 31 to 300 seconds with a mean value of 147 seconds. Nonresponders represented 7% (17/242) of the cases. Myonecrosis post-PCI occurred in 29 patients (12%) and was more common in nonresponders than in normal responders (29% vs 11%, respectively; P = .03 on multivariate analysis). Major adverse cardiac events at 6 months occurred in 13 patients (1 sudden death possibly related to stent thrombosis and 12 post-PCI myocardial infarctions) and were more common in the nonresponder group (12% vs 5%, respectively; P = .06 on multivariate analysis).
Unresponsiveness to clopidogrel as assessed by the point-of-care test PFA-100C/ADP is an independent major risk factor for thrombotic complications after coronary intervention.
American heart journal 03/2010; 159(3):434-8. DOI:10.1016/j.ahj.2009.12.020 · 4.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The PENTRA 60C(+) hematology analyzer provides a complete blood cell (CBC) count, including a five-part differential (5-DIFF) count and two leukocyte subpopulations, i.e. large immature cells (LIC's) and atypical lymphocytes (ALY's). We evaluated its analytical performance and assessed agreement with the ADVIA 2120, in order to install the analyzer in a small satellite hematology laboratory. First we assessed repeatability, reproducibility and carry-over to evaluate the analytical performance. Then we used Pearson correlation coefficients, Passing and Bablok regression analysis and a graphical approach (n = 209) to evaluate agreement with the ADVIA 2120. Repeatability and reproducibility were excellent for the majority of CBC and 5-DIFF count parameters. Carry-over was negligible. Our data showed very good correlation for most CBC count parameters. Lower correlation coefficients were observed for red cell distribution width, mean corpuscular volume and mean platelet volume. As compared to the ADVIA 2120, the 5-DIFF count performed very well. Agreement was poorer for low-level eosinophils and basophils. Furthermore, the PENTRA 60C(+) was equally able to identify pathological blood samples through the determination of LIC's and ALY's. Therefore, the PENTRA 60C(+) is an eligible blood cell counter to be operational in a satellite laboratory setting.
International journal of laboratory hematology 05/2009; 31(2):132-41. DOI:10.1111/j.1751-553X.2007.01011.x · 1.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mild type 1 von Willebrand disease (VWD) is characterized by low to variable penetrance of bleeding, a high (increased) prevalence of blood group O, von Willebrand factor (VWF) values around and above 30% with normal ratios of VWF:ristocetin cofactor activity (RCo)/VWF:antigen (Ag), VWF:collagen binding (CB)/VWF:Ag and factor VIII (FVIII):coagulant activity (C)/VWF:Ag. Within this group of patients, the combination of the C1584 mutation and blood group O is rather frequent. Patients with mild VWD type 1 present good/normal responses of FVIII:C and VWF parameters to desmopressin (DDAVP). With the exclusion of dominant VWD type Vicenza, type 1/2E, recessive 2N and dominant 2M, missense mutations in patients with mild VWD type 1 with normal multimers are mainly located in the regulatory sequence region, the D1/D2 propeptide region, the D' VWF-FVIII binding site region and the D4, B1-B3 and C1-C2 domains but rarely in the D3, A1 or A2 domain. A new category of either dominant or recessive mild VWD type 1 due to mutations in the D4, B1-B3 and C1-C2 domains of the VWF gene consists of two groups: one group with mild VWD with normal VWF multimers and a second group with mild/moderate VWD with smeary multimer pattern.
[Show abstract][Hide abstract] ABSTRACT: A complete set of laboratory investigations, including bleeding time, PFA-100 closure time, factor VIII coagulant activity (FVIII:C), von Willebrand factor (VWF) ristocetin cofactor activity (RCo), collagen binding (CB) and antigen concentration (Ag), ristocetin-induced platelet aggregation (RIPA) and multimeric analysis of VWF in low and medium SDS-agarose resolution gels, is warranted to diagnose and classify all variants of von Willebrand disease (VWD). VWD type 2M and 2U are typically characterized by decreased RIPA and a poor response of VWF:RCo to desmopressin (DDAVP), but normal VWF:CB and good responses of VWF:CB, VWF:Ag and FVIII:C to DDAVP. VWF multimeric analysis in patients with VWD 2M and 2U show relative decreases in large VWF multimers with less resolved triplet structure of each of the multimeric bands in low-, medium- or high-resolution gels. VWD type 2M or 2U are caused by a loss-of-function mutation in the A1 domain. The laboratory manifestations and molecular defects in the A1 domain causing VWD type 2M and 2U are clearly distinct from all variants of type 1 VWD and also from all other variants [VWD type 2A, 2B, 2E (IIE) and 2C (IIC)].
[Show abstract][Hide abstract] ABSTRACT: The detection of even tiny amounts of von Willebrand factor (VWF):antigen after desmopressin treatment or in hidden sites like platelets allows the differentiation between patients with recessive von Willebrand disease (VWD) type 3, severe type 1, and 2C (2A subtype IIC). Recessive VWD 2C of various severity displays a characteristic multimeric pattern with pronounced dimer band, absence of triplet structure and lack of large multimers not due to increased proteolysis. Recessive VWD type 2C (2A subtype IIC) is caused by homozygosity or double heterozygosity of missense mutations in the D1 and D2 domains of the VWF propeptide (pp) that catalyzes the multimerization in the D3 domain at the N terminus of mature VWF. In expression studies of recombinant mutant VWF, secretion of VWF mainly consisted of dimers which failed to form intermediate- and high-molecular-weight multimers consistent with the clinical diagnosis of VWD 2C (2A subtype IIC). Carriers of a heterozygous missense mutation in the VWFpp region (D1-D2 domain) of the VWF gene may present mild VWD type 1 and show a typical multimeric pattern with a heavy predominance of VWF dimers.
[Show abstract][Hide abstract] ABSTRACT: Influence of changes in levels of coagulation factors and anticoagulants on acquired activated protein C (APC) resistance were studied in 40 healthy women during normal pregnancy. Factor VIII (FVIII), von Willebrand factor antigen (VWF:Ag), free protein S (FPS) and protein C were determined at 5-13, 14-26 and 27-40 weeks gestation and more than 6 weeks postpartum. APC anticoagulant activity was determined by measuring the activated partial thromboplastin time before and after adding human APC, expressed as the APC-sensitivity ratio (APC-SR). During the second and third gestation trimesters a significant increase (P < 0.05) in FVIII and VWF:Ag levels and a decrease in FPS levels were seen compared with the first trimester. Postpartum FVIII and VWF:Ag levels significantly decreased and FPS levels increased compared with the third trimester. Protein C levels remained unchanged during pregnancy and postpartum. Between increased FVIII and lowered APC-SR a trend of inverse correlation (r = -0.329; P = 0.076) occurred in the second trimester. No correlation was found between APC-SR and FPS or VWF:Ag levels. A remarkable finding is the strong inverse relationship between APC-SR and protein C levels (r <or= -0.392; P < 0.05) during pregnancy and postpartum. This may indicate that anticoagulant activity of added human APC measured by activated partial thromboplastin time is diminished in the presence of high endogenous protein C levels. A possible hypothesis is steric hindrance by sample protein C of APC binding sites on target activated factor V and/or cofactor protein S. The clinical significance of this finding should be determined because it complicates the interpretation of lowered APC-SR.
[Show abstract][Hide abstract] ABSTRACT: We report the case of a 78-year-old man who presented with acute myeloid leukaemia showing subpopulations of cells expressing platelet-associated markers and the presence of a pan-myeloid component, besides glycophorin A-positive cells. Most of the immature cells had a proerythroblast-like morphology and we classified this case as an FAB-M6 variant, as suggested by Bain (1). According to the WHO classification, this leukaemia fulfilled the criteria of'AML with multilineage dysplasia' (2). Immunophenotyping characteristics showed two distinct aberrant subpopulations, a young pan-myeloid (CD45+ with low density, CD34+, CD117+, CD13+, CD33+, partial cytoplasmic myeloperoxidase (MPO)+) population with platelet-associated markers (CD41+, CD42+, CD61+) and a CD45+, CD117+, CD34- population with partial CD235a positivity indicative for erythroid maturation. This case belongs to the group of 'early' erythroblastic leukaemias where a subset of progenitor cells present with erythroid-megakaryocyte bipotentiality or are blocked at an early BFU-E (burst-forming unit erythrocyte)-like stage of erythroid differentiation (11, 12, 13).
[Show abstract][Hide abstract] ABSTRACT: The current standard set of von Willebrand factor (VWF) parameters used to differentiate type 1 from type 2 VWD include bleeding times (BTs), factor VIII coagulant activity (FVIII:C), VWF antigen (VWF:Ag), VWF ristocetine cofactor activity (VWF:RCo), VWF collagen binding activity (VWF:CB), ristocetine induced platelet aggregation (RIPA), and analysis of VWF multimers in low and high resolution agarose gels and the response to DDAVP. The BTs and RIPA are normal in asymptomatic carriers of a mutant VWF allele, in dominant type 1, and in recessive type 2N VWD, and this category has a normal response of VWF parameters to DDAVP. The response of FVIII:C is compromised in type 2N VWD. The BTs and RIPA are usually normal in type Vicenza and mild type 2A VWD, and these two VWD variants show a transiently good response of BT and VWF parameters followed by short in vivo half life times of VWF parameters. The BTS are strongly prolonged and RIPA typically absent in recessive severe type 1 and 3 VWD, in dominant type 2A and in recessive type 2C (very likely also 2D) VWD and consequently associated with low or absent platelet VWF, and no or poor response of VWF parameters to DDAVP. The BTs are prolonged and RIPA increased in dominant type 2B VWD, that is featured by normal platelet VWF and a poor response of BT and functional VWF to DDAVP. The BTs are prolonged and RIPA decreased in dominant type 2A and 2U, that all have low VWF platelet, very low VWF:RCo values as compared to VWF:Ag, and a poor response of functional VWF to DDAVP. VWD type 2M is featured by the presence of all VWF multimers in a low resolution agarose gel, normal or slightly prolonged BT, decreased RIPA, a poor response of VWF:RCo and a good response of FVIII and VWF:CB to DDAVP and therefore clearly in between dominant type 1 and 2U. The existing recommendations for prophylaxis and treatment of bleedings in type 2 VWD patients with FVIII/VWF concentrates are mainly derived from pharmocokinetic studies in type 3 VWD patients. FVIII/VWF concentrates should be characterised by labelling with FVIII:C, VWF:RCo, VWF:CB and VWF multimeric pattern to determine their safety and efficacy in prospective management studies. As the bleeding tendency is moderate in type 2 and severe in type 3 VWD and the FVIII:C levels are near normal in type 2 and very low in type 3 VWD patients. Proper recommendations of FVIII/VWF concentrates using VWF:RCo unit dosing for the prophylaxis and treatment of bleeding episodes are proposed and has to be stratified for the severity of bleeding, the type of surgery either minor or major and for type 2 and type 3 VWD as well.
[Show abstract][Hide abstract] ABSTRACT: All variants of type 2 von Willebrand disease (VWD) patients, except 2N, show a defective von Willebrand factor (VWF) protein (on cross immunoelectrophoresis or multimeric analysis), decreased ratios for VWF:RCo/Ag and VWF:CB/Ag and prolonged bleeding time. The bleeding time is normal and FVIII:C levels are clearly lower than VWF:Ag in type 2N VWD. High resolution multimeric analysis of VWF in plasma demonstrates that proteolysis of VWF is increased in type 2A and 2B VWD with increased triplet structure of each visuable band (not present in types 2M and 2U), and that proteolysis of VWF is minimal in type 2C, 2D, and 2E variants that show aberrant multimeric structure of individual oligomers. VWD 2B differs from 2A by normal VWF in platelets, and increased ristocetine-induced platelet aggregation (RIPA). RIPA, which very likely reflects the VWF content of platelets, is normal in mild, decreased in moderate, and absent in severe type 2A VWD. RIPA is decreased or absent in 2M, 2U, 2C, and 2D, variable in 2E, and normal in 2N. VWD 2M is usually mild and characterized by decreased VWF:RCo and RIPA, a normal or near normal VWF multimeric pattern in a low resolution agarose gel. VWD 2A-like or unclassifiable (2U) is distinct from 2A and 2B and typically featured by low VWF:RCo and RIPA with the relative lack of high large VWF multimers. VWD type 2C is recessive and shows a characteristic multimeric pattern with a lack of high molecular weight multimers, the presence of one single-banded multimers instead of triplets caused by homozygosity or double hereozygosity for a mutation in the multimerization part of VWF gene. Autosomal dominant type 2D is rare and characterized by the lack of high molecular weight multimers and the presence of a characteristic intervening subband between individual oligimers due to mutation in the dimerization part of the VWF gene. In VWD type 2E, the large VWF multimers are missing and the pattern of the individual multimers shows only one clearly identifiable band, and there is no intervening band and no marked increase in the smallest oligomer. 2E appears to be less well defined, is usually autosomal dominant, and accounts for about one third of patients with 2A in a large cohort of VWD patients.
[Show abstract][Hide abstract] ABSTRACT: The requirement for a safe diagnostic strategy should be based on an overall posttest incidence of venous thromboembolism (VTE) of less than 1%, with a negative predictive value of more than 99 to 100% during 3-month follow-up. Compression ultrasonography (CUS) and spiral computed tomography (CT) currently are the methods of choice to confirm or rule out deep venous thrombosis (DVT) and pulmonary embolism (PE), respectively. CUS has a negative predictive value (NPV) of 97 to 98%, indicating the need to improve the diagnostic work-up of patients with suspected DVT by clinical score assessment and D-dimer testing. Spiral CT as a stand-alone method detects all clinically relevant PEs and a large number of alternative diagnoses. It rules out PE with a NPV of 98 to 99%. Spiral CT is expensive, emphasizing the need to improve the diagnostic work-up of patients with suspected PE by the use of clinical score assessment and D-dimer testing. Clinical score assessment for DVT and PE has not safely ruled out VTE in multicenter studies and in routine daily practices. Modification of the Wells clinical score assessment for DVT by elimination of the "minus 2 points" for alternative diagnosis will improve the reproducibility of the clinical score assessment. The combination of a first negative CUS and a negative SimpliRed or an enzyme-linked immunosorbent assay (ELISA) VIDAS D-dimer of < 1,000 ng/mL safely exclude DVT (NPV > 99%) irrespective of clinical score assessment and without the need to repeat CUS in approximately 60 to 70% of patients. The rapid quantitative and qualitative agglutination D-dimer assays for the exclusion of VTE are not sensitive enough as stand-alone tests and should be used in combination with clinical score assessment. A normal rapid ELISA VIDAS D-dimer test as a stand-alone test safely excludes DVT and PE, with a NPV of 99 to 100%, irrespective of clinical score, without the need of CUS or spiral CT. The combined strategy of a rapid ELISA VIDAS D-dimer followed by objective testing with CUS for DVT and by spiral CT for PE will reduce the need for noninvasive imaging techniques by 40 to 50%.
Seminars in Thrombosis and Hemostasis 10/2006; 32(7):678-93. DOI:10.1055/s-2006-951296 · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The current standard for the diagnosis and management of patients with congenital von Willebrand disease (vWD) includes bleeding times (BTs), PFA-100 closure time (PFA-CT), factor (F) VIII:coagulant activity (C), vWF:antigen (Ag), vWF:ristocetin cofactor activity (RCo), a sensitive vWF:collagen-binding activity (CB), ristocetin-induced platelet aggregation (RIPA), analysis of vWF multimers in low- and high-resolution agarose gels, and the response to desmopressin. Guidelines and recommendations for prophylaxis and treatment of bleedings in vWD patients with vWF/FVIII concentrates should be derived from analysis of the content of these concentrates and from pharmacokinetic studies in different types of vWD patients with severe type 1, 2, or 3 vWD. The vWF/FVIII concentrates should be characterized by labeling with FVIII:C, vWF:RCo, vWF:CB, and vWF multimeric pattern, which will determine their predicted efficacy and safety in prospective management studies. Because the bleeding tendency is moderate in type 2 and severe in type 3 vWD, and because the FVIII:C levels are subnormal in type 2 and very low in type 3 vWD patients, new guidelines using vWF:RCo unit dosing for the prophylaxis and treatment of bleeding episodes are proposed. Such guidelines should be stratified for the severity of bleeding, the type of surgery (either minor or major), and also for the severity and type of vWD (i.e., either type 2 or 3 vWD).
Seminars in Thrombosis and Hemostasis 10/2006; 32(6):636-45. DOI:10.1055/s-2006-949669 · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The most common nonimmune etiology of acquired von Willebrand syndrome (AvWS) includes hypothyroidism, Wilms' tumor, thrombocythemia, or congenital heart defects, and the use of various drugs. AvWS type 1 in patients with hypothyroidism is due to decreased Willebrand factor (vWF) synthesis and is reversible by treatment with thyroxin. AvWS type 1 or 3 in children with Wilms' tumor disappears after successful chemotherapy or tumor resection but the mechanism of the vWF deficiency is unknown. The AvWS type 2 in patients with thrombocythemia of various myeloproliferative disorders is caused by increased proteolysis of large vWF multimers at increasing platelet counts to above 1000 x 10 (9)/L. Reduction of platelet counts to normal results in correction of the vWF parameters together with disappearance of the bleeding tendency. Type 2-like AvWS in children with congenital heart valve defects is caused by shear stress-induced proteolysis of large vWF multimers and is reversible after surgical correction. AvWS associated with the use of drugs disappears after discontinuation of the causative agent. Immune-mediated AvWS is associated with either systemic lupus erythematosus (SLE) or immunoglobulin G (IgG) benign monoclonal gammopathy (BMG), and usually shows a type 2 vWF deficiency. Using a simple enzyme-linked immunosorbent assay, an IgG antibody against vWF is detectable in AvWS associated with SLE and IgG BMG. The IgG-autoantibody-factor (F) vWF/VIII complex is rapidly cleared from the circulation, which explains the combined FVIII:coagulant activity (C) and vWF deficiency and the poor responses of FVIII:C and vWF parameters to intravenous desmopressin acetate and vWF/FVIII concentrates. A transient correction of both FVIII:C and vWF parameters to normal for a few weeks after high-dose intravenous immunoglobulin is seen in AvWS associated with SLE and IgG BMG. AvWS associated with SLE uniformly shows a curative response to corticosteroids. AvWS associated with IgG BMG does not respond to corticosteroids, immune suppression, or chemotherapy. AvWS associated with IgM BMG is rare and does not respond to any conventional treatment.
Seminars in Thrombosis and Hemostasis 10/2006; 32(6):577-88. DOI:10.1055/s-2006-949663 · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Leptin has been associated with disturbances in hemostasis and fibrinolysis, with inconsistent results on the influence of fat mass. However, the influence of the amount of visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (SAT) has not yet been studied. In this study, we investigated the relationship between leptin and fibrinogen, von Willebrand factor antigen (vWF:Ag), and plasminogen-activator inhibitor-1 (PAI-1) activity and determined the influence of associated metabolic variables and VAT versus SAT.
Fibrinogen, vWF:Ag, PAI-1,VAT and SAT (CT-scan), and insulin resistance (homeostasis model assessment; HOMA-IR) were measured in 199 women and 81 men with overweight or obesity visiting the weight management clinic of a university hospital.
Leptin did not relate to fibrinogen (r = 0.11 and 0.13 in women and men respectively; P > 0.05), a relationship with vWF:Ag was only found in men (r = 0.31; P = 0.005), while leptin related to PAI-1 activity in both men (r = 0.36; P < 0.001) and women (r = 0.23; P < 0.001). Further analysis showed leptin to have an effect on the variation of PAI-1 independent of VAT and HOMA-IR in women, but not in men. Multiple regression showed HOMA-IR to be the most important determinant of PAI-1, both in men and women, but leptin also showed an independent effect. As for vWF:Ag, leptin was an independent determinant in men only.
PAI-1 related to leptin levels independent of fat mass percentage, HOMA-IR, and the amount of VAT and SAT. For vWF:Ag this relationship was found only in men, and not in women, while a relationship with fibrinogen could not be demonstrated.
European Journal of Endocrinology 09/2006; 155(3):477-84. DOI:10.1530/eje.1.02239 · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To investigate whether leukocyte count, fibrinogen, von Willebrand factor (vWF) and plasminogen activator inhibitor-1 activity (PAI-1) are increased in subjects with the metabolic syndrome as defined by the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATPIII) and the World Health Organisation (WHO).
A total of 520 overweight and obese subjects: 379 women and 141 men, visiting the weight management clinic of a University Hospital. Subjects and measurements:Waist circumference, triglycerides, HDL cholesterol, blood pressure and fasting glucose were determined, and the presence or absence of the metabolic syndrome according to the NCEP-ATPIII criteria was assessed. In 349 subjects, data on the waist-to-hip ratio (WHR) and albumin excretion rate were available and the WHO criteria were applied. Insulin resistance was defined using the HOMA-IR index.
Subjects with the metabolic syndrome according to the NCEP-ATPIII criteria had significantly higher levels of leukocyte count (P < 0.001) and PAI-1 (P < 0.001), while no significant differences were found for fibrinogen or vWF (P > 0.05). Using the WHO criteria, similar results were found except for vWF, where higher levels were found in subjects with the metabolic syndrome. When subjects were classified according to the number of components of the metabolic syndrome, levels of leukocyte count, vWF and PAI-1 activity were significantly different (P < 0.05). In logistic regression analysis PAI-1, gender and leukocyte count were independent determinants of the metabolic syndrome (P < 0.001).
Evidence for being a true component of the metabolic syndrome is strong for PAI-1, less for leukocyte count and weak for vWF and fibrinogen.
International Journal of Obesity 08/2006; 30(8):1308-14. DOI:10.1038/sj.ijo.0803189 · 5.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recessive type 3 von Willebrand disease (VWD) is caused by homozygosity or double heterozygosity for two non-sense mutations (null alleles). Type 3 VWD is easy to diagnose by the combination of a strongly prolonged bleeding time (BT), absence of ristocetine-induced platelet aggregation (RIPA), absence of von Willebrand factor (VWF) protein, and prolonged activated partial thromboplastin time (aPTT) due to factor VIII:coagulant (FVIII:C) deficiency. VWD type 3 is associated with a pronounced tendency to mucocutaneous and musculoskeletal bleedings since early childhood. Carriers of one null allele are usually asymptomatic at VWF levels of 50% of normal. Recessive severe type 1 VWD is caused by homozygosity or double heterozygosity for a missense mutation. Recessive type 1 VWD differs from type 3 VWD by the presence of detectable von Willebrand factor: antigen VWF:Ag and FVIII:C levels between 0.09 and 0.40 U/mL. Patients with recessive type 1 VWD show an abnormal VWF multimeric pattern in plasma and/or platelets consistent with severe type 2 VWD. Carriers of a missense mutation may have mild bleeding and mild VWF deficiency and can be diagnosed by a double VWF peak on cross immunoelectrophoresis (CIE). There will be cases of mild and moderate recessive type 1 VWD due to double heterozygosity of two missense mutations, or with the combination of one missense mutation with a non-sense or bloodgroup O. Mild deficiency of VWF in the range of 0.20 to 0.60 U/mL, with normal ratios of von Willebrand factor: ristocetine cofactor/antigen VWF:RCo/Ag and VWF:collagen binding/antigen (VWF:CB/Ag), normal VWF multimers, and a completely normal response to desmopressin acetate (DDAVP) with VWF level rising from below to above 1.00 U/mL are very likely cases of so-called pseudo-VWF deficiency in individuals with normal VWF protein and gene. Autosomal dominant type 1 VWD variants are in fact type 2 variants caused by a heterozygous missense mutation in the VWF gene that produces a mutant VWF protein that has a dominant effect on normal VWF protein produced by the normal VWF allele with regard to the synthesis, processing, storage, secretion, and/or proteolysis of VWF in endothelial cells. A DDAVP challenge test clearly differentiates between dominant type 1 VWD phenotype and dominant type 2 M VWD.
[Show abstract][Hide abstract] ABSTRACT: Microvascular disturbances in essential thrombocythemia (ET) and polycythemia vera (PV), including erythromelalgia, and atypical and typical transient cerebral, ocular, and coronary ischemic attacks, are caused by platelet-mediated transient and occlusive thrombosis in the end-arterial circulation. ET patients with microvascular disturbances have shortened platelet survival, increased beta-thromboglobulin (beta-TG), platelet factor 4 (PF4), and thrombomodulin (TM) levels, and increased urinary thromboxane B2 (TXB2) excretion, indicating platelet-mediated thrombotic processes. Inhibition of platelet cyclooxygenase-1 by aspirin is followed by relief of microvascular disturbances; correction of shortened platelet survival; correction of increased plasma beta-TG, PF4, and TM levels; and correction of increased TXB2 excretion to normal. In PV associated with thrombocythemia, increased hematocrit and whole blood viscosity aggravate the platelet-mediated microvascular syndrome of thrombocythemia to produce major arterial and venous thrombotic complications. Correction of hematocrit to normal by phlebotomy will reduce the major arterial and venous thrombotic complications, but fails to prevent the platelet-mediated microvascular circulation disturbances in PV patients because thrombocythemia persists. Complete relief and prevention of microvascular and major thrombosis in ET and PV patients, in addition to phlebotomy, are obtained by treatment with aspirin and not with coumarin. The discovery of JAK2 V617F gain of function mutation in patients with myeloproliferative disorders (MPDs) expands our insights into the molecular etiology and biological features of ET, PV, and chronic idiopathic myelofibrosis (CIMF). The current concept is that heterozygous JAK2 V617F mutation with increased kinase activity is enough for megakaryocyte proliferation and increased hypersensitive platelets with no or slightly increased erythropoiesis in ET and in early PV mimicking ET. Homozygous JAK2 mutation with pronounced kinase activity is associated with trilinear megakaryocyte, erythroid, and granulocytic myeloproliferation, myeloid metaplasia, and secondary myelofibrosis (MF), with the most frequent clinical picture of classical PV complicated by major thrombosis in addition to the platelet-mediated microvascular thrombotic syndrome of thrombocythemia. The positive predictive value of a JAK2 V617F polymerase chain reaction test for the diagnosis of MPDs is high (near to 100%), but only half of ET and MF (sensitivity 50%) and the majority of PV (sensitivity 85 to 97%) are JAK2 V617F positive. Bone marrow histopathology, when used in combination with specific markers such as serum erythropoietin, PRV-1, endogenous erythroid colony formation, peripheral blood parameters and red cell mass, has a high sensitivity and specificity (near 100%) to detect the early and overt stages of the MPDs and to differentiate between ET, PV, and CIMF in both JAK2 V617F-positive and -negative MPDs.
Seminars in Thrombosis and Hemostasis 05/2006; 32(3):174-207. DOI:10.1055/s-2006-939431 · 3.69 Impact Factor